IPv6 MTU discovery

Thanks to http://muzso.hu/2009/05/17/how-to-determine-the-proper-mtu-size-with-icmp-pings it looks like it's easy to discover the IPv6 MTU (Maximum Transmission Unit):


$ ping6 -c1 -M do -s 10000 www.google.com  | grep mtu | awk '{ print $NF }' 

mtu=1500

So the IPv6 MTU to www.google.com is 1500.

From another system, the MTU is 1480:

$ ping6 -c1 -M do -s 10000 www.google.com  | grep mtu | awk '{ print $NF }'

mtu=1480

Easy, isn't it?

For old-skool IPv4, the output of ping is a bit different, so the awk parsing is a bit different:

$ ping -c1 -M do -s 10000 www.google.com | grep mtu | awk '{ print $NF }' | sed -e s/\)//

1500

HTH

Dutch ISP Telfort introduces IPv6

After conducting an IPv6 pre-pilot (see http://ipv6-or-no-ipv6.blogspot.nl/2012/01/dutch-isp-telfort-conducting-ipv6-pre.html), Dutch ISP pilot Telfort has silently introduced IPv6 for all its DSL (VDSL and ADSL) customers. I don't know about its FttH customers. And mobile customers probably have to wait.

Telfort's IPv6 is opt-in; you have to enable it in your Zyxel modem. This is how:

• Log in on your Zyxel modem at http://192.168.1.254/ 
• Go to Network Setting -> Broadband. At the top of that page, check which connection is used: VDSL or ADSL. Then find that entry in the table below, and click on the corresponding "Modify" icon on the far right
• In the windows that pops up, at "IPv6/IPv4 DualStack" click enable. More below, enable "6to4 Tunneling" and check "6RD Enable". Then click the Apply button
• Final check: the column IPv6 should now be on "enable" at your VDSL or ADSL line.

That's it. You should now have IPv6. Check via http://ip6.nl/ or http://test-ipv6.com/. If not, reboot your  modem and computer once.

Technology used is 6RD. Address prefix is 2A00:CD8::/32

Telfort's mother company KPN yet has to introduce IPv6.